U.S. patent number 7,449,789 [Application Number 11/397,019] was granted by the patent office on 2008-11-11 for light-emitting device, planar light source and direct type backlight module.
This patent grant is currently assigned to Hon Hai Precision Industry Co., Ltd.. Invention is credited to Ga-Lane Chen.
United States Patent |
7,449,789 |
Chen |
November 11, 2008 |
Light-emitting device, planar light source and direct type
backlight module
Abstract
A light-emitting device (12) includes a base (14) and two red
light-emitting chips (22), two green light-emitting chips (24) and
a blue light-emitting chip (26) arranged on the base red, green,
blue, green, red in a left-to-right order. The red light-emitting
chips, the green light-emitting chips and the blue light-emitting
chip include a plurality of red-color quantum dots, green-color
quantum dots and blue-color quantum dots respectively. A planar
light source (10) includes a planar plate (102), and a plurality of
the light-emitting devices arranged in an array on the planar
plate. A direct type backlight module (20) includes a diffusing
sheet (18) and the planar light source facing a surface of the
diffusing sheet.
Inventors: |
Chen; Ga-Lane (Fremont,
CA) |
Assignee: |
Hon Hai Precision Industry Co.,
Ltd. (Tu-Cheng, TW)
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Family
ID: |
37947345 |
Appl.
No.: |
11/397,019 |
Filed: |
April 3, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070085092 A1 |
Apr 19, 2007 |
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Foreign Application Priority Data
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Oct 14, 2005 [TW] |
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94135972 A |
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Current U.S.
Class: |
257/791; 257/102;
257/13; 257/88; 257/89; 257/E25.02; 257/E25.028; 257/E33.001;
257/E33.008; 257/E33.077; 257/E51.018 |
Current CPC
Class: |
B82Y
10/00 (20130101); G02F 1/133603 (20130101); F21K
9/00 (20130101); H01L 25/0753 (20130101); H01L
33/06 (20130101); H01L 2924/0002 (20130101); H01L
2924/0002 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
H01L
33/00 (20060101) |
Field of
Search: |
;257/79-103,13,E51.018,E33.001,E25.028,E51.022 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Louie; Wai-Sing
Assistant Examiner: Armand; Marc
Attorney, Agent or Firm: Cheng; Andrew C. Chung; Wel-Te
Claims
What is claimed is:
1. A light-emitting device comprising: a base; two red
light-emitting chips each comprising a first semiconductor layer
formed on the base, a p-type gallium arsenide layer formed on the
first semiconductor layer, gallium arsenide phosphide layer formed
on the p-type gallium arsenide layer, an n-type gallium arsenide
layer formed on the gallium arsenide phosphide layer, and a
plurality of red-color quantum dots being formed in the gallium
arsenide phosphide layer; two green light-emitting chips each
comprising a second semiconductor layer formed on the base, a
p-type aluminum gallium indium phosphide layer formed on the second
semiconductor layer, an undoped aluminum gallium indium phosphide
layer formed on the p-type aluminum gallium indium phosphide layer,
an n-type aluminum gallium indium phosphide layer formed on the
undoped aluminum gallium indium phosphide layer, and a plurality of
green-color quantum dots being formed in the undoped aluminum
gallium indium phosphide layer; a blue light-emitting chip
comprising a third semiconductor layer formed on the base, a
gallium nitride nucleation layer formed on the third semiconductor
layer, a p-type gallium nitride layer formed on the gallium nitride
nucleation layer, an indium gallium nitride layer formed on the
p-type gallium nitride layer, an n-type gallium nitride layer
formed on the indium gallium nitride layer, and a plurality of
blue-color quantum dots being formed in the indium gallium nitride
layer; wherein the red light-emitting chips, the green
light-emitting chips, the blue light-emitting chip are arranged on
the base red, green, blue, green, red in a left-to-right order.
2. A planar light source comprising: a planar plate; a plurality of
light-emitting devices arranged on the planar plate in an array,
each light-emitting device comprising a base; two red
light-emitting chips each comprising a first semiconductor layer
formed on the base, a n-type gallium arsenide layer formed on the
first semiconductor layer, a gallium arsenide phosphide layer
formed on the p-type gallium arsenide layer, an n-type gallium
arsenide layer formed on the gallium arsenide phosphide layer, and
a plurality of red-color quantum dots being formed in the gallium
arsenide phosphide layer; two green light-emitting chips each
comprising a second semiconductor layer formed on the base, a
n-type aluminum gallium indium phosphide layer formed on the second
semiconductor layer, an undoped aluminum gallium indium phosphide
layer formed on the p-type aluminum gallium indium phosphide layer,
an n-type aluminum gallium indium phosphide layer formed on the
undoped aluminum gallium indium phosphide layer, and a plurality of
green-color quantum dots being formed in the undoped aluminum
gallium indium phosphide layer; a blue light-emitting chip
comprising a third semiconductor layer formed on the base, a
gallium nitride nucleation layer formed on the third semiconductor
layer, a n-type gallium nitride layer formed on the gallium nitride
nucleation layer, an indium gallium nitride layer formed on the
p-type gallium nitride layer, an n-type gallium nitride layer
formed on the indium gallium nitride layer, and a plurality of
blue-color quantum dots being formed in the indium gallium nitride
layer; wherein the red light-emitting chips, the green
light-emitting chips, the blue light-emitting chip are arranged on
the base red, green, blue, green, red in a left-to-right order.
3. A direct type backlight module comprising: a diffusing sheet; a
planar light source arranged facing a surface of the diffusing
sheet, the planar light source comprising a planar plate; and a
plurality of light-emitting devices arranged on the planar plate in
an array, each light-emitting device comprising a base; two red
light-emitting chips each comprising a first semiconductor layer
formed on the base, a p-type gallium arsenide layer formed on the
first semiconductor layer, a gallium arsenide phosphide layer
formed on the p-type gallium arsenide layer, an n-type gallium
arsenide layer formed on the gallium arsenide phosphide layer, and
a plurality of red-color quantum dots being formed in the gallium
arsenide phosphide layer; two green light-emitting chips each
comprising a second semiconductor layer formed on the base, a
p-type aluminum gallium indium phosphide layer formed on the second
semiconductor layer, an undoped aluminum gallium indium phosphide
layer formed on the p-type aluminum gallium indium phosphide layer,
an n-type aluminum gallium indium phosphide layer formed on the
undoped aluminum gallium indium phosphide layer, and a plurality of
green-color quantum dots being formed in the undoped aluminum
gallium indium phosphide layer; a blue light-emitting chip
comprising a third semiconductor layer formed on the base, a
gallium nitride nucleation layer formed on the third semiconductor
layer, a p-type gallium nitride layer formed on the gallium nitride
nucleation layer, an indium gallium nitride layer formed on the
p-type gallium nitride layer, an n-type gallium nitride layer
formed on the iridium gallium nitride layer, and a plurality of
blue-color quantum dots being formed in the indium gallium nitride
layer; wherein the red light-emitting chips, the green
light-emitting chips, the blue light-emitting chip are arranged on
the base red, green, blue, green, red in a left-to-right order.
Description
BACKGROUND
1. Technical Field
The invention generally relates to a light-emitting device, a
planar light source and a direct type backlight module.
2. Discussion of Related Art
Nowadays, liquid crystal materials are widely utilized in various
liquid crystal displays (LCDs) having different sizes for different
applications, such as TVs, liquid crystal projectors, mobile
telephones, personal digital assistants (PDAs), etc. Since liquid
crystal itself cannot emit light, light sources must be utilized to
irradiate/illuminate liquid crystal for image display. The light
sources are called backlight sources because they are usually
configured behind liquid crystal panels. A combination of all
components behind the liquid crystal panels, including the light
sources, is generally referred to as a backlight module. Usually,
backlight modules can be classified into edge type backlight
modules and direct type backlight modules.
Edge type backlight modules are usually utilized in middle sized or
small sized LCDs, such as LCDs used in mobile telephones. Direct
type backlight modules are usually utilized in large sized LCDs,
such as LCDs used in TVs. In direct type backlight modules, a
plurality of cold cathode fluorescent lamps (CCFLs) are generally
used as light sources. The plurality of CCFLs are linear and
arranged parallel to each other. Due to the spacing between the
LCDs, the resulting light source is discontinuous. The CCFLs may
also have differences in brightness and chroma between each other
such that the illumination of the direct type backlight module is
poor. As well as this, the CCFLs contain mercury, making them
difficult and dangerous to dispose of safely.
What is needed, therefore, is a light-emitting device, a planar
light source and a direct type backlight module with uniform
brightness and chroma.
SUMMARY
A light-emitting device according to one preferred embodiment
includes a base, two red light-emitting chips, two green
light-emitting chips and a blue light-emitting chip. The red
light-emitting chips, the green light-emitting chips and the blue
light-emitting chip include a plurality of red-color quantum dots,
green-color quantum dots and blue green-color quantum dots
respectively. The red light-emitting chips, the green
light-emitting chips, the blue light-emitting chips are arranged on
the base in red-green-blue-green-red formation.
A planar light source according to another preferred embodiment
includes a planar plate, and a plurality of the light-emitting
devices arranged on the planar plate in an array.
A direct type backlight module according to another preferred
embodiment includes a diffusing sheet and the planar light source
opposite a surface of the diffusing sheet.
Compared with conventional CCFLs, this light-emitting device has
following advantages. Quantum dot energy level in the
light-emitting device can have different quantum levels. The
bandwidth can be controlled in a more narrow way so that it is
easier to distinguish between the individual light beams emitted
from each quantum dot. Furthermore, light-emitting device having
quantum dots are more environmentally friendly.
Advantages and novel features will become more apparent from the
following detailed description of the present light-emitting
device, planar light source and direct type backlight module, when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the present light-emitting device, its related
planar light source and direct type backlight module can be better
understood with reference to the following drawings. The components
in the drawings are not necessarily drawn to scale, the emphasis
instead being placed upon clearly illustrating the principles of
the present light-emitting device, its related planar light source
and direct type backlight module. Moreover, in the drawings, like
reference numerals designate corresponding parts throughout the
several views.
FIG. 1 is a schematic, top view of a light-emitting device in
accordance with a first preferred embodiment;
FIG. 2 is a schematic, cross-sectional view taken along line II-II
of FIG. 1;
FIG. 3 is a schematic, top view of a planar light source in
accordance with a second embodiment; and
FIG. 4 is a schematic, side view of a direct type backlight module
in accordance with a third embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
References will now be made to the drawings to describe preferred
embodiments of the present light-emitting device, its related
planar light source and direct type backlight module, in
detail.
Referring to FIGS. 1 and 2, a light-emitting device 12 in
accordance with a first embodiment is shown. The light-emitting
device 12 includes a base 14, two red light-emitting chips 22, two
green light-emitting chips 24 and a blue light-emitting chip
26.
The red light-emitting chips 22, the green light-emitting chips 24
and the blue light-emitting chip 26 are arranged on the base 14 in
red-green-blue-green-red pattern from left to right. The red
light-emitting chips 22, the green light-emitting chips 24 and the
blue light-emitting chip 26 include a plurality of red-color
quantum dots, green-color quantum dots and blue-color quantum dots
respectively. The base 14 is made from glass plate or quartz glass
plate.
The red light-emitting chip 22 includes a first semiconductor layer
104, a p-type gallium arsenide layer 106 formed on the first
semiconductor layer 104, a gallium arsenide phosphide layer 108
formed on the p-type gallium arsenide layer 106 and an n-type
gallium arsenide layer 110 formed on the gallium arsenide phosphide
layer 108. The plurality of red-color quantum dots are formed in
the gallium arsenide phosphide layer 108. The first semiconductor
layer 104 serves as a supporting layer for the red light-emitting
chip 22. The first semiconductor layer 104 is made of a material
which may be selected from a group consisting of gallium phosphide,
gallium arsenide and gallium aluminum arsenide.
The green light-emitting chip 24 includes a second semiconductor
layer 112, a p-type aluminum gallium indium phosphide layer 114
formed on the second semiconductor layer 112, an undoped aluminum
gallium indium phosphide layer 116 formed on the p-type aluminum
gallium indium phosphide layer 114 and an n-type aluminum gallium
indium phosphide layer 118 formed on the undoped aluminum gallium
indium phosphide layer 116. The plurality of green-color quantum
dots are formed in the undoped aluminum gallium indium phosphide
layer 116. The second semiconductor layer 112 serves as a
supporting layer for the green light-emitting chip 24. The second
semiconductor layer 112 is made of a material which may be selected
from a group consisting of gallium phosphide and gallium
arsenide.
The blue light-emitting chip 26 includes a third semiconductor
layer 120, a gallium nitride nucleation layer 122 formed on the
third semiconductor layer 120, a p-type gallium nitride layer 124
formed on the gallium nitride nucleation layer 122, an indium
gallium nitride layer 126 formed on the p-type gallium nitride
layer 124 and an n-type gallium nitride layer 128 formed on the
indium gallium nitride layer 126. The plurality of blue-color
quantum dots are formed in the indium gallium nitride layer 126.
The third semiconductor layer 120 serves as a supporting layer for
the blue light-emitting chip 26. The third semiconductor layer 120
is made of a material which may be made from a material selected
from a group consisting of aluminum oxide, silicon carbide, zinc
selenide and zinc sulfide.
The quantum dots may be manufactured by a bottom up process or a
top down process. In the case of the bottom up process, they are
formed in a high vacuum thin film growth chamber with chip
substrate materials like gallium arsenide, indium phosphide, zinc
sulfide, cadmium selenide, gallium nitride, gallium or aluminum
oxide etc. There are four gas lines with mass flow rate controllers
and valves. A CVD (chemical vapor deposition) process can be used,
such as MOCVD (metal organic chemical vapor deposition), thermal
CVD or PECVD (plasma enhanced chemical vapor deposition) etc, or
the MBE (molecule beam epitaxy) process. For MOCVD, the gas can be
Ammonia, Trimethylinduum, Trimethylgallium, or Silicon Hydride. The
CVD temperature can be as high as 1200.degree. C. The quantum dots
growing directly from the bottom up.
In the case of the top down process for manufacturing quantum dots,
firstly a quantum well structure is provided on a chip substrate.
Secondly a photoresistant layer is spin-coated onto the quantum
well. Thirdly, the photoresistant layer is exposed and developed to
create the quantum dot patterning. Finally the photoresistant layer
is etched by wet etching or dry etching to form dot shaped quantum
dots. The chip substrate materials such as gallium arsenide, indium
phosphide, gallium nitride, zinc sulfide, or cadmium selenide etc.
III-V or IV-VI materials in periodical table can be used to form
the quantum dots.
Quantum energy level of quantum dot can have different quantum
levels. The bandwidth of quantum dot can thus be controlled more
narrowly so that the individual light beams emitted from each
quantum dot are easier to distinguish from each other, compared to
conventional light-emitting chips and CCFL. Furthermore, this
structure is more environmentally friendly than conventional
designs as it is constructed of less harmful material.
Referring to FIG. 3, a planar light source 10 in accordance with a
second embodiment is shown. The planar light source 10 mainly
includes a planar plate 102 and a plurality of light-emitting
devices 12 provided by the first embodiment.
The light-emitting devices 12 are arranged on the planar plate in
an array to form the planar light source 10.
Referring to FIG. 4, a direct type backlight module 20 in
accordance with a third embodiment is shown. The direct type
backlight module 20 includes a diffusing sheet 18 and a planar
light source 10 provided by the second embodiment.
The planar light source 10 is arranged facing a surface of the
diffusing sheet 18. Due to the easily distinguishable light emitted
from the light-emitting chips, the direct type backlight module 20
emits light with uniform brightness and chroma, creating good
illumination for the LCD. The red light, green light and blue light
emitted from the planar light source 10 are fully mixed in the
diffusing sheet 18 and emerge as white light from the diffusing
sheet 18. White light and light of other colors different from the
three primary colors can be obtained by mixing the three primary
colors in the diffusing sheet 18. With quantum dot light-emitting
devices, color presentation on LCDs may exceed current NTSC
(National Television Systems Committee) specification by 20%.
Furthermore, as is known to those skilled in the art, the direct
type backlight module 20 may further optionally include one or more
optical elements (not shown), such as a polarizer and/or a
brightness-enhancing plate stacked over the diffusing sheet 18.
It is to be understood that the above-described embodiment is
intended to illustrate rather than limit the invention. Variations
may be made to the embodiment without departing from the spirit of
the invention as claimed. The above-described embodiments are
intended to illustrate the scope of the invention and not restrict
the scope of the invention.
* * * * *